Machined Aluminum Research Articles

A New Quantitative Sensitivity Analysis of the Flow Stress of 18 Engineering Materials in Machining

It has long been argued about which effect, among the effects of strain hardening, strain-rate hardening, and temperature softening, is predominant in governing the material flow stress in machining. This paper presents a new quantitative sensitivity analysis of the flow stress of 18 engineering materials based on the well-known Johnson-Cook model. It is demonstrated that the first predominant factor governing the material flow stress is either strain hardening or thermal softening, depending on the specific material employed and the varying range of temperatures. Strain-rate hardening is the least important factor governing the material flow stress, especially when machining aluminum alloys.

Analysis of laser micro drilled holes through aluminium for micro-manufacturing applications

Conventional laser machining of aluminium with long wavelength lasers has its inherent problems due to the high reflectivity of aluminium to laser radiation (Handbook of Optics, vol 1, 2nd ed. New York: McGraw-Hill; 1995). Laser processing at shorter wavelengths reduces the reflectivity of the workpiece to the incident laser radiation and can also reduce the dimensions of the obtainable machining geometries. This paper reviews the limiting factors in the micro machining of aluminium using a diode pumped solid state (DPSS) Nd:YAG laser operated at 1064, 532, and 355 nm. The geometries of the laser-machined samples were investigated using interferometric, and optical methods to assess how the processing fluence and wavelength will affect the obtainable precision for successful integration of the laser in a micromachining CAD/CAM system.

Tribological and dry machining evaluation of superhard TiB 2/TiC multilayer coatings deposited on Si(001), M2 steel, and C3 WC cutting tool inserts using magnetron sputtering

TiB 2/TiC multilayer coatings were synthesized in a dual-cathode unbalanced magnetron sputter–deposition system with substrate rotation. Our previous research has demonstrated that all coatings on M2 steel are polycrystalline with TiB 2(001) preferred orientation and have a layer structure. Compressive stress in these coatings is less than 2 GPa, with hardness up to 60 GPa, which corresponds to 100% hardness enhancement over the rule-of-mixture value. This paper concentrates on the tribological and dry machining evaluation of these coatings. Coatings were deposited on Si(001), polished M2 steel, and C3 WC cutting tool inserts. From dry block-on-ring tribotesting, the 3:0.5 multilayer (i.e., the layer thickness is 3.0 nm for TiB 2 and 0.5 nm for TiC) coating provides four times improvement in wear resistance over the uncoated M2 steel substrate. In addition, dry machining was performed using AISI 1018 steel and 319 aluminum alloy cylindrical workpieces. Monolithic TiB 2 and 3:1 multilayer coatings (i.e., the layer thickness is 3.0 nm for TiB 2 and 1.0 nm for TiC) have the best performance: the flank wear was reduced by about a factor of ten compared with the uncoated tool after a cutting distance of 600 m. Results from cutting force measurements demonstrate that as far as dry machining is concerned, there is no direct correlation among cutting forces, room-temperature hardness, and flank wear. In dry machining of aluminum, the carbide tool deposited with the 3:1 multilayer, unlike other tools, has negligible buildup on the rake face. This results in better and more consistent surface finish of the final workpiece and less likelihood for premature tool breakage.

Transfer of 319 Al alloy to titanium diboride and titanium nitride based (TiAlN, TiCN, TiN) coatings: effects of sliding speed, temperature and environment

In order to develop coatings to be used in dry machining aluminum alloys, it is necessary to have a better understanding of the factors that influence transfer and adhesion of aluminum to the surfaces of coatings that are potential candidates for this function. In this work, the material transfer and adhesion phenomena between 319 Al alloy samples and different coatings deposited on M2 type steel substrates were examined using a pin-on-disc type wear machine. The coatings included titanium diboride (TiB 2), CrN, titanium nitride based compounds, (TiN, TiCN, TiAlN) and uncoated M2 steel discs. The effects of sliding speed, sliding distance, test temperature and working atmosphere were studied. Sliding distances were kept short because the focus of the work was on the initial transfer behavior. The effect of surface roughness was examined using two TiB 2 coatings; one with an R a value of 16nm and the other with a large R a of 83 nm. The morphology of sliding tracks was examined using a scanning electron microscope (SEM). With the aid of image analysis software, the SEM images were used to rank the coatings according to the amount of aluminum transferred and the loose debris generated during the tests. In general, the TiB 2 and TiCN coatings exhibited the least amount of aluminum transfer on their surfaces compared to the other coatings. TiN and CrN exhibited the largest amount of aluminum transfer, but the amount of loose debris generated on the surfaces of these two coatings was small. Increasing the sliding speed from 0.12 to 0.6 m/s led to a decrease in the amount of aluminum transferred to the surfaces of all the coating tested. Increasing the test temperature to 160 °C did not significantly change the amount of aluminum transferred to TiB 2 and TiCN coatings. However TiN, TiAlN, CrN and M2 steel picked up significantly less aluminum compared to that at room temperature. When tested under argon atmosphere, all coatings (except TiB 2) exhibited a sharp decrease in the amount of aluminum adhered to their surfaces suggesting that the presence of oxygen and water vapor promoted aluminum adhesion to these coatings. The amount of aluminum transfer to the TiB 2 coating was a weak function of the inertness of the environment, which was attributed to the high chemical stability of TiB 2. Surface roughness played a critical role in aluminum transfer, especially in the early stages of sliding of TiB 2.

Rapid prototyping in the development of optical pickup unit

Rapid prototyping (RP) has already proven itself in the electronics industry as a method for shortening the product development time cycle. In the development of the optical pickup unit (OPU), extremely high precision is needed to make a functional model. Very often, in the design phase of the product development cycle, the prototype of the OPU is machined from a single piece of aluminium block to make the working sample. In this project, a comparison of the machined aluminium sample, RP samples from various RP processes and that moulded out from the injection moulding machine is made on surface finishing as well as dimensional accuracy. Finally, a comparison of tooling cost, piece part cost and lead time of obtaining the parts is also discussed on the different prototyping and manufacturing processes.

Cutting performance of DLC coated tools in dry machining aluminum alloys

The purpose of this study is to examine the impact of tribological properties of DLC coatings on cutting performance. In this work, DLC was prepared on a cemented carbide substrate by using a vacuum arc discharge with a graphite cathode. DLC was identified as a non-hydrogenated amorphous carbon film with the thickness of 0.1 μm. DLC coatings were evaluated in a pin-on-disk test as well as in aluminum alloy machining. DLC had a low friction coefficient (0.1) against aluminum alloy and an excellent anti-adhering property. The results showed that DLC coated tools can be used to reduce adhesion between a tool and a work material, and the formation of a built-up edge. In order to analyze the cutting process, a finite element method (FEM) simulation at the tool–chip interface was employed, to compare the experimental evidence. In particular, the comparison was carried out taking into account the chip shapes and cutting force. The FEM simulation of a chip formation process was in qualitative agreement with the experiments, and this enabled an explanation of the phenomenon of the cutting process. In the case of dry machining of the aluminum alloys, DLC coatings enhance the tool performance, the machined surface integrity and the tool life compared to an uncoated tool.

A Computer-Aided Design Tool in Java for Planar Gripper Design

We describe an Internet-based CAD tool that automatically designs gripper jaws that will rotate a given rigid convex polygonal part from a selected stable resting orientation to a desired final orientation to facilitate insertion or assembly. In this paper we describe the CAD algorithm, its Java implementation, and improvements that relax input specifications and improve computational efficiency. We illustrate with physical experiments using a machined aluminum part and the resulting gripper as designed by the CAD tool. We also consider cases where a solution may not exist and derive a class of triangular parts that cannot be rotated with the planar grippers. The CAD tool, implemented as a Java applet, is available online at www.ieor.berkeley.edu/∼goldberg/sa-gripper/.

Use of Recycled Steel Machining Chips and Aluminum Can Shreds for Synthesizing Iron Aluminide Intermetallic Alloys

Some iron aluminide intermetallic alloys based on Fe 3 Al or FeAl have been synthesized from recycled raw materials of steel machining chips and aluminum can shreds. The former was an industrial waste made at a bearing case maker, and it had a spiral shape and a length less than 1 mm and contained 0.87 wt% C, 0.21 wt% Si, 1.53wt% Cr with some other minor elements. The latter, on the other hand, was made by shredding used aluminum cans, and it had a flaky shape and a edge length of 2 to 3 mm and contained 2.3wt% Mg, 0.36 wt% Fe, 0.88 wt% Mn with some other minor elements. When compacts of the steel and aluminum mixture were heated in a crucible in an argon atmosphere, they exothermically reacted and produced iron aluminide intermetallic alloys. For comparison, similar alloys were produced from pure iron and aluminum by melting them in the same heating apparatus. The bending strength, fracture toughness, Vickers hardness and wear resistance of the alloys synthesized from the recycled raw materials were more excellent than or similar to those of the alloys produced from pure iron and aluminum.

704 アルミナセラミックスの機械加工性の改善(切削・研削・研磨加工)

704 アルミナセラミックスの機械加工性の改善(切削・研削・研磨加工)

205 DLCコーティング工具によるアルミ合金の切削加工(第2報) : 成膜条件が被削材に及ぼす影響(GS-13 加工(2))

Development of coated tool is activity performed in recent years for the purpose of extending tool life and application for cutting of high hardness and high toughness material in order to acquire a machined surface side by stabilizing the cutting edge. However, in case of cutting ductility material, such as aluminum alloy, it is easy to occur cohesion of chips, and that causes chipping of cutting edge. These are causes of material chipping on cutting edge. Then, Application of the Diamond-like carbon (DLC) film was considered, DLC film has outstanding properties such as high hardness, chemical resistance and low friction coefficient under various conditions. DLC films were discussed the hardness and scratch tests to machine aluminum ally in this study.

Experimental design and investigation of a pin-type reconfigurable clamping system for manufacturing aerospace components

This paper presents an experimental design and evaluation of a pin-type universal clamping system. The clamping system is designed for holding complex-shaped aerospace components, such as turbine blades, during machining processes. The experimental investigation is performed by comparing the pin-type clamping system with a dedicated clamping system during the machining of aluminium and steel parts. Force signals are monitored during machining. The experimental results are presented and compared with a dedicated clamping system. From the comparison, the performance of the clamping system is discussed. The results provide an evaluation of the designed pin-type clamping systems for machining operations. The results prove that the pin-type clamping system can be reconfigured for machining different complex shaped components with performance comparable with a dedicated clamping system.

On the optimisation of machining parameters for dry drilling of aeronautic aluminium alloy

Machining aluminium alloys without lubrication seriously increases the tool wear because of the severe tribological conditions at the tool/chip interface. Indeed, metal cutting generates high temperatures and pressures due to the high strain rate (≥10 4 s -1 ) and the friction between the tool and the chip. Thus, it is very important to be able to clearly identify the parameters influencing the machining quality. In order to study dry drilling with W-Co carbide tools, experiments were conducted using different drill geometries and varying cutting conditions. The workpiece material used in this work is the aluminium alloy 2024 T-351. Optimised drill geometries can be deducted from experimental results to obtain holes with an aerospace quality. The following parameters were used to evaluate the holes quality: the minimum and maximum diameter deviations, the burr height and the surface roughness. The microscope observation of the tool rake face shows that the main damage is adhesion and diffusion wear revealing the presence of high temperature. Cutting conditions were tested and chosen to limit the tool damage and by consequence to increase the tool life.

523 Development of an Electrochemical Machining Method for Machining Curved Holes

A method has been developed for machining the coolant channels of molds and other types of curved holes using the simplest possible equipment. This method focuses on the use of a flexible tool to machine a curved hole by following a small hole formed by the same tool, instead of applying an actuator to control the tool shape. It was confirmed in machining tests that the curvature and shape of curved holes can be controlled by varying the rotational speed of the electrode and the electrolyte pressure. An investigation was made of the machining speed, taking into account the application of the new method to actual molds. It was found that a machining speed of approximately 2 mm/min was the limit when machining aluminum. This speed limitation is due to the boiling of the electrolyte around the electrode because of the heat generated during machining. Moreover, in actual machining operations, it is necessary to measure the position of a curved hole as it is being machined. Accordingly, an investigation was also made of a method for measuring the position of the electrode while machining a curved hole.

High‐resolution laboratory lysimeter for automated sampling of tracers through a 0.5 m soil block

A computer-controlled, automated sample collection from a 0.5-m lysimeter, designed to give superior temporal and spatial resolution for monitoring the movement of chemical tracers through a large undisturbed soil block, is described. The soil block, 0.520.520.5 m, was monitored for saturation using eight time domain reflectometry probes. Rainfall was applied at approximately 1600 ml hm1 using a 12212 array of 23-gauge (0.318 mm internal diameter) hypodermic needles. Soil leachates were collected at the base of the soil block using a machined aluminium collection plate with a 10210 grid of funnels that passed leachates to sample collection palettes. Sample collection was automated using a personal computer equipped with National Instruments LabVIEW™ software and linked to sensors for palette tracking. The automation of the lysimeter allowed sample collection and storage over a user-defined period with no human interaction. As an example of the use of the automated lysimeter, results show the distribution of phosphate within the soil. The eluted phosphate showed an initial and secondary peak, and only emerged from preferential flow channels.

DEVELOPMENT OF A VARIABLE FLOW STRESS MACHINING THEORY FOR ALUMINIUM ALLOYS

This paper describes the development of a variable flow stress predictive machining theory for aluminium alloys. This theory is based on the Oxley's machining theory which allows for the high strain-rate/high temperature flow stress and thermal properties of the work materials and has so far been applied and tested for plain carbon steels. The developed predictive theory for aluminium has been applied in predicting cutting forces, chip thicknesses, etc., for a wide range of cutting conditions (cutting speeds ranging from 100 to 1000 m/min) when machining two alloys: one with 97.64%Al and the other with 93.89%Al (a free machining aluminium alloy). The flow stress properties required in applying the predictive method were obtained from bar turning test results and by applying the machining theory in reverse. For the above mentioned aluminium alloys, a comparison between predicted and experimental cutting force results shows good agreement.

Dry turning of alumina/aluminum composites with CVD diamond coated Co-cemented tungsten carbide tools

Triangular (TPGN 160308) WC–6 wt.%Co inserts having different average grain sizes (1 and 3 μm) were submitted to surface roughening either by wet etching with Murakami's reagent or by a heat treatment in the hot filament chemical vapour deposition (HFCVD) reactor. The heat treatment was performed in a monohydrogen-rich atmosphere at substrate temperatures as high as 1000 °C. Scanning electron microscopy and energy-dispersive spectroscopy showed that this pre-treatment led to surface roughening of the as-ground inserts and to a lower surface Co concentration. Prior to deposition, all inserts were etched with an acid solution of hydrogen peroxide. Diamond coatings were deposited by HFCVD. The coated inserts were tested by dry machining of aluminum–matrix composite (Al–10%Al 2O 3) bars. Turning test results indicated that a proper combination of substrate pretreatment and microstructure can significantly improve tool life.

Studies on fretting wear: influence of rubbing surface materials and some considerations

When a small tangential relative displacement is repeatedly made between surfaces to which a quasi-static normal force is applied, fretting fatigue or fretting wear are induced. There are many factors influencing these fretting phenomena. In this study, fretting wear is observed experimentally for various surface material combinations, and fretting wear volume is estimated through a newly proposed method. The influence of surface materials on fretting wear is made clear by estimating the fretting wear size, fretting wear volume and cross-sectional area configuration of the wear scar. Four plate specimen materials are used in the experiment. They are a carbon steel for machine structural use, aluminum alloy, cemented carbide and Sialon ceramics.

Dielectric measurement on magnesium aluminum silicate glass–ceramics prepared by different routes

Synthesis of machinable quality magnesium aluminum silicate (MgO-Al 2O 3-SiO 2) for fabrication of insulators/spacers usable in high-voltage applications under high vacuum conditions has been carried out following two different routes, i.e., (a) sintering route and (b) glass route. The dielectric constant ( ε′) and the dielectric loss ( D=tan δ) have been measured in MAS glass–ceramics (GC) at different temperatures for frequencies up to 12 MHz. The analyses for these samples indicate that dielectric constant variation with frequency exhibits an initial drop in the lower frequency region followed by slight increase at higher frequency. The influence of temperature on dielectric constant is discussed.

On the machining of alumina and glass

Machining of electrically non-conducting materials like alumina and glass is still a major problem. Electrochemical spark machining (ECSM) process is a potential process for machining these materials. However, ECSM has its own inherent limitations. So far, only ordinary cutting tools have been used during ECSM by previous researchers, but the results obtained are not as good as anticipated. In the present work, electrochemical spark abrasive drilling (ECSAD) experiments have been conducted using abrasive cutting tools, with a view to enhance the capabilities of the process. Use of an abrasive cutting tool, when compared to a conventional cutting tool, has been found to improve the process performance, viz. enhanced material removal and increased machined depth. The workpiece materials used are alumina and borosilicate glass.

Development of high performance diamond-coated drills for cutting high silicon aluminum alloy

In machining aluminum alloy that contains a large amount of silicon, highly wear-resistant cutting tools such as diamond coated ones are needed because silicon particles in the matrix of aluminum quickly wear the tools. However, diamond coatings on cutting edges actually debond off easily. In this paper, we examined two possibility in order to improve the adhesion of diamond coatings on cutting edges. One is to optimize the construction of coated drills by changing the shape of cutting edges as well as coating thickness. Another is improvement of the toughness of diamond coatings. By putting together the results obtained, the diamond-coated drills with optimized structure were newly developed. Their performance appeared to be satisfactory in cutting high silicon aluminum alloy.